# Illustration Law of the Lever applied to a seesaw

The law of the lever demonstrated on a seesaw. Shown in green is the part of the lever called the force arm. And shown in blue is the part of the lever called the load arm. The force arm has length $$l_1$$, measured to the pivot point (shown in red). And the load arm has the length $$l_2$$.
There is a mass on the load arm that is subjected to a force $$F_2$$. This can be, for example, the gravitational force that pulls the mass to the ground. To lift the mass on the seesaw, we must act on the force arm with a force $$F_1$$. The longer the force arm, the smaller this force $$F_1$$ must be. This means that it is easier to lift a mass with a longer force arm. This is the law of leverage. As a formula, we can write it as follows:$$F_1 \, l_1 ~=~ F_2 \, l_2$$